Transient electromagnetic sounding (TEM) is the basic method of electric survey applied for solving problems of structure and ore, oil-and-gas prospecting. The non-stationary electromagnetic sounding proved to be highly efficient when applied in prospecting/surveying in geology. In complicated hard geological settings, when seismic methods fail to provide reliable geological results, the electric survey is of particular importance. Its benefits are described as:
TEM is highly productive in investigating geo-electric section at a moderate conductivity of sedimentary cover (<200 Ohm); it has the highest resolution amongst the methods of electromagnetic sounding.
The TEM curves are extremely not sensitive to non-horizontal heterogeneities and impact of high-resistance screens;
Possibility to use only the time domain of sounding;
Application of devices with minimum spacing;
A large dynamic range of a signal;
When using the multi-channel telemetric devices, the TEM sounding has a high performance and efficiency;
The non-stationary sounding may be applied for solving geological problems in 2-D, 3-D and 4-D versions, both in summer and winter periods.
The telemetric stations SGS-TEM and FastSnap have been successfully employed for electric survey since 1998 by the staff of Irkutsk Electric Survey Enterprise and «SibGeoSystems» Company at Novosibirsk. In terms of TEM sounding, creation of multi-channel telemetric systems of recording, their high mobility and reliable gauging proved the electric sounding technologies to be at the highest rate of accuracy, performance and efficiency.
Multi-channel telemetric electric survey station SGS-TEM
Effective and reliable tool for gauging by electromagnetic sounding (TEM, FS, direct current method).
Ensures high performance of electric survey in any physical-geographic and climatic conditions.
The recording system with arithmetic sampling increment and powerful mathematic algorithms of data processing ensures an enhanced noise immunity of equipment.
Mobile telemetric recorders provide the possibility to arrange arbitrary observation nets with a high spatial density.
The company-developed software provides serviceable and high-performance operations with voluminous data at all stages of field and office observations.
Features of telemetric electric survey station SGS-TEM
• Simultaneous recording of signals of electromagnetic field emplacement from several field receivers (spatially spaced from each other);
• Location of amplifying channels and analog-to-digital converter (ADC) directly from receiver loop allows avoiding problems of transmitting analog signals, raising data quality and noise immunity;
• In available gauges the built-in GPS receivers accurately take account of geometry of devices;
• GPS- based high-precision system of synchronization;
• Small dimensions and a set of field modules make the station mobile and allow the receiver loops to be located away from roads and observations to be arranged within the zone from 3 to 5 km under conditions of rugged relief. The station lets 10 and more gauges to be connected, spacing may reach 1 km. Personnel is capable of conducting comprehensive monitoring with a high spatial-temporal density;
• Telemetric gauges have built-in accumulators of 6 V voltage supporting intense field operations of modules for 3-4 days. All gauges are charged automatically and simultaneously from powerful accumulators 12 V or circuit 220 V.
JSC «IREP» jointly with «SibGeoSystems» Company at Novosibirsk offer the software developed for solving geological problems in different fields of geoelectric prospecting. All programs were introduced and tested in production, and therefore they take into account demands and requirements of a wide circle of electric surveyors. Integration of powerful mathematic algorithms, means of visualization, utilization of effective databases and friendly user interface meet the demands of the most experienced specialists, as well as those who only get acquainted with electric survey technologies. The program complexes include modules for:
· Geoinformation support of electric survey;
· Topographic tie-up of maps, exchange of data with GPS-receivers, planning measurement grid;
· Recording and preliminary processing of data;
· Interpretation of results, mathematic modeling;
· Plotting diagrams, sections and maps.
The recording equipment and field techniques, applied for complex geo-electric sections, meet the requirements of electric survey of high resolution with enhanced space-time density of measurements. During field operations the signals of field emplacement are recorded with a high degree of sampling, which improves quality of sounding and helps to introduce highly effective mathematical algorithms of noise suppression. A high accuracy of synchronization, frequent arithmetic signal sampling interval, preservation of all signal realizations predetermined the feasibility to survey in industrial regions, where TEM sounding was not previously employed.